Currently, a piezo element using a ferroelectric material such as lead zirconate titanate (Pb(Zr, Ti)O3: PZT) is applied to an MEMS (Micro Electro Mechanical Systems) technique such as an inkjet head an acceleration sensor.
Particularly, a PZT film has been attracted attention and actively researched by various organizations (Patent Document 1 to 3).
Various research has been conducted in order to improve withstand voltage characteristics of a PZT film.
Hereinafter, a conventional situation before the invention is achieved will be described.
Firstly, regarding the layered structure shown in FIG. 13, particularly, in the case of manufacturing a layered structure having the first electroconductive layer 3, the dielectric layer 4, and the second electroconductive layer 5 which are sequentially layered therein on a main surface of the substrate 2 so as to coat the entire region of the main surface by use of a sputtering method, it was studied what kind of problems occur.
FIGS. 14A to 14C are cross-sectional views schematically showing steps of forming the layered structure shown in FIG. 13.
FIG. 14A shows a step A of forming the first electroconductive layer 3 on the substrate 2.
FIG. 14B shows a step B of forming the dielectric layer 4 so as to coat the first electroconductive layer 3.
FIG. 14C shows a step C of forming the second electroconductive layer 5 so as to coat the dielectric layer 4.
FIGS. 15A and 15B are cross-sectional schematic views showing a sputtering apparatus used to carry out the analysis.
FIG. 15A is a cross-sectional view showing the entire film formation apparatus.
FIG. 15B shows the relevant part near the substrate 2 in the film forming chamber.
Conventionally, since the layered structure shown in FIG. 13 is formed on a substrate in the steps shown in FIGS. 14A to 14C in order, a substrate 100 (W) is disposed as shown in FIG. 15B.
Specifically, the top surface (a main surface) of a flat plate-shaped substrate W on which films are to be formed faces the target 21, and the back surface of the substrate W (the other main surface) is mounted on the upper surface of a support 101 (S1).
Moreover, a first adhesion-preventing plate 104 is arranged on the region located at the side portion of the substrate W on the upper surface of the support 101 (S1).
The first adhesion-preventing plate 104 functions to prevent a film from being formed on the upper surface of the support 101 (S1).
For this reason, normal film formation is carried out on the entire top surface of the substrate W; however, the phenomenon that sputtered particles pass through a slight space between the side surface of the substrate W and the first adhesion-preventing plate 104 and are adhered to the periphery thereof may occur, and there is a possibility that an unexpected film is formed on not only the side surface of the substrate but also the back surface close to the side surface.
In the case of the adhesion of sputtered particles as mentioned above, after the film formation, it is necessary to provide a superfluous step of removing the portion at which adhesion of the particles occurs, and therefore there is a problem in that manufacturing processes become complicated or the cost of manufacturing increases.
Furthermore, in the case where a layered structure includes a specified layer therein that is made of a film containing “a chemical element having a high vapor pressure (for example, Pb, Mg, Zn, Mn, Li, K, Na, Tl, Sm, Sr, Yb, or the like)”, there is also a problem as follows.
Particularly, “a chemical element having a high vapor pressure” is scattered from the specified layer during film formation or after film formation, the element is incorporated into the film other than the specified layer and affects the film characteristics (for example, electrical characteristics, mechanical characteristics, or the like) of the film other than the specified layer. Furthermore, in the case where the layered structure constitutes a device or the like, it is difficult for the characteristics of the device to fall within a desired numerical value range, and there is a possibility that a stabilized manufacturing line cannot be realized.